Nuclear, Reactors

Nuclear Outage Operational Excellence

Issue 8 and Volume 113.

The U.S. nuclear fleet faces a tough outage schedule this fall, but there are ways to manage scarce resources.

By Nancy Spring, Senior Editor

The U.S. nuclear fleet is getting ready for a busy outage season this fall. Besides basic refueling outages, there are three steam generators and one reactor head replacement scheduled.

“You see a lot of work to keep the units healthy, to expand their output and extend their lives,” said Andy Patterson, a partner in the utilities practice at Oliver Wyman, a global general management consulting firm.

Fuel inspection at the South Texas Project station, preparing for the fall outage. Photo, Justin Daily, STP.
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Research by Oliver Wyman shows that outage costs can account for up to 25 percent of total annual O&M budgets. Direct costs associated with refueling outages can exceed $800,000 per day and additional lost margins for time off-line can top $500,000 per day. U.S. nuclear reactors shut down once every 18 to 24 months to refuel, so efficiencies and best practices can really pay off.

The U.S. nuclear power industry has a reputation for operational excellence in the nuclear world. The nuclear industry in this country has significantly improved safety and performance over the past few decades, increasing plant reliability and “substantially increasing electricity generation output without adding new capacity,” according to a January 2009 Electric Power Research Institute (EPRI) white paper. EPRI found that in the last 20 years, performance improvements in the U.S. nuclear fleet were equal to building 27 new 1,000 MW nuclear plants.

But some of the biggest management challenges come not when a plant is up and running but when it’s down for outages. That’s when the plant owner is exposed to financial and operational risk ranging from the caliber of project management to the price of replacement power and supply chain disruption.

The logistics of taking a nuclear plant off-line, completing the scheduled projects and refueling and then re-synching it to the grid are incredibly complex and involve thousands of people.

“The level of activity increases exponentially,” said Carl Parry, president of Utilities Service Alliance (USA), a cooperative of 15 U.S. utilities that operate 27 reactors and 17 power stations, comprising 26 percent of the U.S. nuclear industry. “It’s like a 32- or 36-day Indy pit stop, 24/7.”

Of the Alliance’s 27 units, 12 will be down this fall, with the first one going off-line in early September.

Outage Logistics

The Nuclear Energy Institute (NEI) says the average refueling outage in the U.S. was 38 days, an improvement over the industry average in the 1980s and 1990s of three months. (See Table 1 for more recent duration averages.) Parry said that for the spring outage season the average time for USA’s members is 36 days.

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Patterson cites Institute of Nuclear Power Operations’ (INPO) analysis that shows refueling outage durations in the U.S. for pressurized and boiling water reactors may be creeping up.

“Clearly, the U.S. is the best operating fleet in the world, but the durations of the outages have been difficult to sustain, much less drop,” he said.

Patterson said the INPO data would have to be carefully normalized to account for some numbers that could skew it, but several factors make him believe there has been an increase in outage duration.

With experienced people leaving and new people coming in on both the utility and contractor side, it’s hard to sustain high levels of excellence. “What you’ll find with these plants is that there’s a level of intimacy that’s required to really understand all the details about what needs to be done,” he said.

At the same time it’s difficult to get highly productive craft labor, sparking intra-industry competition and driving up labor costs.

“What we’re seeing is as the workforce ages, and labor and components get more expensive, the duration as well as the cost move up a bit,” said Patterson.

One big challenge is managing the congestion caused by thousands of laborers converging on a site all at once. Ramp rates to absorb all the different classes of workers have to be looked at carefully.

“The best operators have that down to a science,” he said.

Always Open For Suggestions

Patterson said one of the pluses for nuclear companies planning outages is their historically good track record. To build on that strategically, he recommends integrating business plans with outage plans.

Allowing enough time for planning and execution of an outage can be tricky, but benchmarking can be done on all kinds of tasks, such as how long it takes to put up scaffolding. Then plants can compare themselves with other operators.

Clarifying a labor strategy for in-house staff versus in-house fleet-wide shared resources versus contractor employees also is important to eliminate sources of delay or scope change or creep. Just having people who are badged and familiar with the site is a huge advantage and the more aggressive programs will use their own workers for a large portion of the labor needed, said Patterson.

“If you’re a single-site operator, that’s easy to say but hard to do,” said Patterson. “But if you’re an Exelon, you have economies of scale that give you an advantage. An outage is a very complex task and a very different animal depending on the scale and scope of your operation.”

That’s one of the reasons the Utilities Services Alliance was formed, said Parry, to help single unit nuclear operators gain the economies of scale that larger organizations enjoy. On the supply side, USA has a portfolio of contracts for products and services that give members volume pricing and closer relationships with suppliers. Supplies and services cover a wide gambit including valve replacement, replacement parts and leasing test equipment.

Suppliers work with USA members on scheduling resources, too.

“This is very important, because one of the challenges we have in our industry is dwindling resources as far as the availability of experienced contract personnel to help us with our refueling outages,” said Parry.

More “graybeards” that helped build this generation of plants are retiring, on the utility and supplier side.

“It seems like each outage season there is a particular discipline that challenges us,” said Parry. “For several outage seasons it was welders, when a lot of the plants were doing large component replacements or power uprates or modifications that required a large number of nuclear-qualified welders. Demand outstripped availability.”

Parry said USA is now working to mitigate a similar condition with health physics technicians by collaborating with the supplier community to grow the next generation of health physics technicians. All USA member plants (see Table 2) are agreeing to take on more junior technicians to support the current outages so they can get the experience they need.

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For Parry, the nuclear renaissance new build is good news and bad news.

“It’s good that the country recognizes the value of the technology, but at the same time we are already struggling with the challenge of manning the plants,” he said. “We, like a lot of industries, are turning our focus to staff and career development for engineers, operations and crafts by working with the junior colleges and universities to offer the necessary curriculums.”

Another way USA addresses the labor problem is through its shared employee team, which lays out the schedule for the outages so that resources can be loaned from one plant to another. The program began with the alliance’s inception in 1996.

Data shows that shared employee productivity is 2 to 2.5 times higher than their contract counterparts.

“This program is very successful,” said Parry. “The station that borrows these folks is receiving high quality personnel who have been trained. There’s a level of expertise and professionalism that you just can’t get.”

Parry acknowledged that the employee sharing program provides a very small percentage of the people needed; out of the 400 to 600 contract workers that are brought in for a typical refueling outage, 15 may be utility people available through the lending program.

“It’s not a silver bullet but because they’re more than two times as productive, it’s beneficial,” said Parry. Plus, the program also promotes cooperation and networking in the industry. A similar USA plan allows plants to share tools and equipment.

At the South Texas Project (STP) electric generating station 90 miles southwest of Houston, Texas, the outage management team launched a suggestion contest as part of its outage management plan to encourage staff involvement in efforts to improve outage safety, performance and efficiency.

An as-is model of key outage tasks and how they are performed was graphically represented on a sheet of brown paper where suggestions and questions could be logged by personnel. Prizes were awarded for the best suggestions.

“We have our established and traditional ways of doing outage work but those may not be the best methods possible,” said outage manager Norm Mayer. “We’re looking for focused, specific comments with as much detail as possible to improve our safety, performance and processes and to reduce exposure and dose.”

STP plans to launch Phase 2 of the suggestion project during the fall outage.

One thing that could ease pressure on strained resources is adjusting outage start and stop dates. Outages are concentrated in the spring and fall, with some stacked on top of each other. The competition for scarce resources—sometimes parts but mainly people—can spark a bidding war that drives up prices.

“The nuclear plants are critical baseload and we want them on in winter and summer, that’s why outages are scheduled for the spring and fall,” said Parry. “But the plants could work together and move their start or stop dates just one week.”

With outage schedules figured in days now not months, uncovering new economies with that kind of fine-tuned timetable is possible, and, based on the U.S. nuclear fleet’s exceptional operational history, probable.

STP’s Fall Outage a Busy One

Work includes replacement of the reactor vessel head.

Workers inspecting nuclear fuel assemblies at the South Texas Project in preparation for the fall outage. Photo, Justin Daily, STP.
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The fall outage at the South Texas Project (STP) electric generating station includes several first-time projects, among them replacement of the reactor vessel head.

STP’s ambitious replacement reactor vessel head (RVH) project has been in development since 2005, when contract negotiations began. The RVHs are being replaced because the current head adapters are made of Alloy 600, which is subject to primary water stress corrosion cracking. The new head adapters will be Alloy 690.

The RVH in STP’s Unit 1 will be replaced in the 2009 fall outage while Unit 2’s RVH is slated for replacement next spring.

STP is one of the newest and largest nuclear power plants in the country, located about 90 miles southwest of Houston, Texas. The plant’s two reactors produce 2,700 MW of electricity and have maintained a net capacity factor of 98.87 percent from 2006 to 2008. The units went online in August 1988 and June 1989.

The heads being replaced are original equipment and were forged in seven separate pieces that were welded together. The new heads are single-piece forgings. Japan Steel Works, one of the few facilities in the world that can handle jobs of this scale—each head is 18 feet 2 inches in diameter and weighs 192.5 tons—did the casting, shaping and rough machining. Mitsubishi Heavy Industries (MHI) completed the manufacturing.

Careful outage management planning has characterized the project since its inception. STP and Westinghouse developed three design change packages a year in advance of the outage, which STP says is a first in the industry. And when the new reactor vessel head went through final pre-service inspection and an area of interest was identified in one of the tube penetrations, STP and Westinghouse industry experts performed additional inspections to make sure the area would not affect the safety or long-term reliability of the new vessel head.

In June, MHI shipped the RVH. The 325-ton “package” will arrive in the Port of Houston and then travel over land to the South Texas Project on a heavy-load trailer outfitted with dozens of wheels. Delivery is scheduled on or before August 21.

More major outage projects are planned for the fall at Unit 1, including:

  • The engineered safety feature transformer for Echo One Bravo will be replaced with a new design that has an auto-tap changer to ensure proper voltage to the safety train bus. STP expects the project to take about nine days.
  • A reactor vessel 10-year in-service inspection, in which the welds in the reactor vessel will be checked, will be performed while the vessel head is removed. This is the second such inspection since Unit 1 went on-line in 1988.
  • A second round of reactor coolant pump motor replacements will begin during the fall outage with the 1 Delta motor. The 8,000 hp motor will be replaced and the old motor refurbished.
  • A 15-year integrated leak rate test will be performed by raising the air pressure in the containment building then measuring the rate at which the pressure drops, or leaks, from the building.
  • All four main steam isolation valves will be inspected and modified.

The South Texas Project Nuclear Operating Company (STPNOC) manages the plant for its owners, who share its energy in proportion to their ownership interest: Austin Energy, 16 percent, CPS Energy, 40 percent, and NRG Energy, 44 percent.